Flashback-proof gas burner



Nov. 18, 1952 L, D .CNTA ErAL 2,618,322

FLASHBACK-'PROOF' GAS BURNER INVENTORS LEWIS D. CONTA JOHN TETI y BY ZZ 'ATTORNEYS Nov. 18, 1952 L D CONTA ETAL 2,618,322

FLAsHBAcK-PROOF GAS BURNER Filed uarch 19, 1949r l l 2 SHEETS- SHEET 2 INVENTOR LEWI CON JO TET I ATTORNEYS Patented Nov. 18, 1952 FLASHBACK-PROOF GAS BURNER Lewis D. Conta, Rochester, N. Y., and John Teti, Plainfield, N. J., assignors to Air Reduction Company, Incorporated, a corporation of New York Application March 19, 1949, Serial No. 82,313

12 Claims. (Cl. 158-27.4)

This invention relates to gas burners, especially those of the oxyacetylene type, such as torches used for cutting, Welding, name-treating and similar operations.

One of the problems that has always confronted the gas-burner art generally. and the oxyacetylene cutting, welding and flame-treating art in particular, is the prevention of backres and flashbacks. While these terms are sometimes used synonymously, there is a well recognized distinction between them, and when used in the distinguishing Way, the term backfire means a recession of the flame, usually explosive, into the torch or burner; and the term ilashback means a continued burning of the iiame somewhere Within the torch or burner upstream from its normal position at the burner oriice. 'I'he two terms as used herein are intended to have these distinctive meanings. A flashback for even a few seconds may overheat a torch so badly that it becomes useless. Moreover, in the case of acetylene, the ashback may cause dissociation which may even occur upstream from the place where the gases meet to form a combustible mixture, thus constituting a special hazard. A backfiraif controlled, is not particularly harmful or dangerous, but a ashback is likely to be both destructive and dangerous.

The principal object of this invention is to provide a gas burner or torch in which backfire is controlled and flashback is impossible.

This object is attained by constructing the burner so that the volume of mixed gases is kept down to an amount that is harmless, thereby controlling backfire, and by providing means for quenching the products of combustion resulting from a backfire and eliminating all points at which the flame could reignite and be sustained in the burner, thereby eliminating the possibility of flashback.

The accompanying drawings illustrate several forms of a burner embodying the invention all of which have the same basic flashback-proof construction;

In the drawings:

Figure 1 is a transverse vertical section taken through a simple form of a flashback-proof multi-name burner embodying the invention;

Fig. 2 is a longitudinal vertical section taken along line 2-2 of Fig. 1;

Fig. 3 is a longitudinal horizontal section taken along line 3-3 of` Fig. 1;

Figs. 4, 5 and 6 are fragmentary sectional views similar to Fig. 3 illustrating three differ- 2 ent modications that may be made in the gas passage arrangement employed in the burner of Figs. 1-3;

Fig. 7 is a transverse vertical section through another form of a flashback-proof burner embodying the invention;

Fig. 8 is a longitudinal horizontal section taken along line 8-8 of Fig. 7 y

Fig. 9 is a fragmentary sectional view similar to Fig. 8 illustrating a modication that may be made in the gas passage arrangement of the burner of Figs. 7 and 8;

Fig. 10 is a transverse vertical section of a circular burner having a gas passage arrangement analogous to that employed in the burner of Figs. 1-3;

Fig. 1l is a horizontal section taken along the line of Fig. 10;

Fig. 12 is a vertical transverse section through another form of burner embodying the invention and having a gas passage arrangement also analogous to that employed in the burners of Figs. 1-3;

Fig. 13 is a sectional view corresponding to Fig. 10 illustrating a circular burner having a gas passage arrangement analogous to that employed in the burner of Figs. 7 and 8;

Fig. 14 is a horizontal section taken along the line |4|4 of Fig. 13; and

Fig. 15 is a vertical transverse section through a burner similar to that shown in Fig. 12 and also having a gas passage arrangement analogous to that employed in the torch of Figs. 7 and 8.

Figs. 1, 2 and 3 illustrate a burner embodying the invention in a simple form. It comprises a block 20 through which manifolding or distributing chambers 2| and 22 are drilled. One of the two gases to be mixed, such as oxygen, is admitted to one end of the distributing chamber 2| through a supply conduit 23 (Fig. 3). other end of the distributing chamber 2| is closed by a plug 24. The other gas, such as acetylene, is admitted to one end of the distributing chamber 22 through a supply conduit 25, the other end of this distributing chamber being closed by a plug 26. The oxygen from the distributing chamw ber 2| passes down through a series of supply passages 2l to a flat shallow recess 28 formed in the lower face of the block 20. Similarly, the acetylene from the distributing chamber 22 passes down through a series of supply passages 29 to the same recess 28. Another block 30 is secured to the lower face of the block 2|) by any suitable means, thus covering the recess 28 at its lower side and making a narrow slot passage of the 3 recess. A row of discharge passages or passageways 3| is formed in the block 3|) so that they communicate with slot passage 28, as best shown in Figs. 1 and 3. The discharge passages 3| lead to the discharge face 33a of the burner where they terminate in discharge orifices. Thus it will be seen that the oxygen and acetylene delivered to the distributing chambers 2| and 22 enter the slot passage 28 Vthrough the supply passages 27 and 29, the oxygen entering the slot passage at its left side as viewed in Fig. 1 and the acetylene entering the slot passage at its right side. The two gases flow inwardly towardv each other until they meet and then now downwardly through. the. I

property on the fact that the slot 28"has one dimension d which does not exceed a critical value at or below which. any gas, mixture in the slot will not burn. This does. not mean that the slot passage will halt ame propagation or detonation, butV it is sufficiently narrow to prevent the gases from continuing to burn in it. or at the upper ends of the discharge passages 3 The absolute value of the dimension d varies for different gases and orifice sizes. It has been found that the maximum value the' dimension d should have for an oxyacetylene burner is in the range from .012 to .016. The exit area through which the gases leave the slot passage 28 is the product of the circumference of the discharge passages 3| times d. For the gas flow involved, this area is suiciently small to keep thegas velocity at this point above the ameblow-away point.

When the burner is constructed in this manner` a flashback is impossible for theA following reasons: When a backfire `occurs the burning gas mixture in the discharge passages 3| will be forced backwards through the slot passage 28 and possibly even up into the supply passages 2l and- 29 leading to it. All of the gas mixture burns, after which the flame goes out. As soon as the pressure wave subsides, the burned gasesY are forced downstream again by the incoming oxygen and acetylene. The only place the fresh incoming gases could possibly burn would bein the discharge passages 3| or possibly in the slot passage 28 immediately adjacent the entrance to these discharge passages since these are the only places where a mixture of the two gases is present. 'I'he slot passage d is so narrow that the gases cannot continue to burn in it, as above described, probably because of the quenching effect of the walls of the slot passage on the gases. Where the gases mix and pass into the discharge passages 3| their Velocity is too high to maintain the lla-me at this place. The discharge passages 3| are sufficiently smooth-walled to prevent a flame from hanging in them. Therefore, any llame fed by the gases after they mix will tend to recede to the entrance end of the discharge passages 3| or to blow out to the exit ends of these passages. Since it is impossible for the flame to be sustained at the entrance end of the discharge passages 3| due to the high gas velocity at this place, it will automatically return to the discharge orifices where the discharge passages 3| open through the discharge face of the burner. In most cases products of combustion from the backfire will becooled sufficiently by the quenching action of the walls of theslot 28 to prevent them fromreigniting the fresh incoming gases whenl they 4 mix. Therefore, the flame is automatically extinguished following a backfire, and the gas mixture discharged at the discharge face of the burner must be reignited by the operator unless reignition automatically takes place by the hot workpiece.

In theburner illustrated inFigs. 1-,3,*a1l of the gas` passing through the supply passagesl and 29 feeds all of the discharge passages 3| since the slot passage 28 places all of the passages 2l and 29 in communication with all of discharge passages 3|.. While this is the simplest satisfactory constructiom a preferred gas passage arrangement is, illustrated in Figs. 4, 5 and 6. In the'gas passagefarrangement shown in Fig. 4 there are a number of slot passages 28' of critical dimension d instead of just one, and each of them places one oxygen supply passage 27 and the corresponding acetylene supply passage 29 in communication with one discharge passage 3|. This has two advantages. First,i it assures equal distribution of the gases tothedischarge passages and therefore assures sufcientgasy velocity atV the entrance to each of the discharge'passages.'

l Secondly, it restricts the volume/of gas 'mixture that can be aiected' by a backfire through any one of the discharge, passages to the volume of gas handled by oner of the relatively small slot passages 28' and, the single discharge passage which it feeds, thereby proportionately reducing the effects of the backfire.

According to the gas passage arrangement shown in Fig. 5, each slot passage 28" made wider than the slot passage shown in Fig. 4 andA places two oxygenv` supply passages 2 and two correspondingacetylene supply passages 23` in communication with. a singleoutlet passage 3 l,

In the gasl passage arrangement illustrated in Fig. 6 the slot passagesare the same as those shown in Fig. 5 but each of them places one oxygen supply passage 21 and the corresponding acetylene supply'p'assage'ZS in communication with a pair of discharge passages 3|.

Figs.v 7 and 8 illustrate a modied form of' burner in which the two gases are delivered sepa-.- rately tov the slot'passage but they are mixed in the slot passage before they reach the dischargev passages leading to the discharge face 'of the burner. A block 32 has two oxygen manifoldingi or distributing chambers 33 and 34 and an ace-- tylene distributing chamber 35 which may be formed in the blocl: in the same manner asthe; distributing chambers 2| and 22 .of the burners previously described. Another block 33 having a series of discharge passages or passagelfays leading Vto the discharge face 36a of the burner forms with a shallow'recess in thelower face of the block 32 a slot passage 38 similar to the slot passage shown in Fig. land having a dimension a. which does notexceed the above-mentionedv critical value. A rowV of oxygen supply'passages 3,9 lead from the oxygen distributing chamber 33' to one side of the slot passage 3.8 and another rowA of oxygen supply passages il lead from' the oxygen distributing chamber Seto` the other side of the slot passage. Two rows of acetylene supply passages M and 42 lead from the `acetylene distributingv chamber 35 to the slot passage 38` and these deliver acetylene to the slot passagesA etopposite sides or themedian' une of the 'slot passage. Since the oxygen and acetylene'aredelivered Separately to the slot passage they do not mix before the gases reach the ,slot passagebutl it will be clear that. an cxyaetylene mixture-is formed in Mthe left Side of the slot4 .passage "as,

viewed in Fig. '7 by the oxygen and acetylene supplied through the passages 39 and 4I, and that an oxyacetylene mixture is also formed in the right side of the slot passage by the oxygen and acetylene supplied through the passages lil and 42. The gas mixture formed in each side of the slot passage then flows toward the discharge passages 3l' where it meets the gas mixture formed in the other side of the slot passage and the total mix ture flows down through the passages 3l to the discharge face of the burner. Thus, instead of the gas mixture being formed at the entrance to the discharge passages and in the discharge passages themselves as in the burners illustrated in Figs. 1-6, it is formed in the slot passage itself, although the two gases are delivered separately to the slot passage as in the case of the burners previously described, and hence there is no gas mixture upstream of the slot passage. Therefore, when a baclire occurs a flashback is prevented in thesame way as described ink connection with the burner illustrated in Figs, 1-3.

The gas passage arrangement in the slotmixing type of burner illustrated in Figs. 7 and 8 is amenable to the same modifications as the gas passage arrangement employed in the burner of Figs. 1-3, one of such modiiications being illustrated in Fig. 9 which is comparable to that illustrated in Fig. 4.

A burner of the type in which the gases mix in the discharge passages but which produces a ring of frames is illustrated in Figs. 10 and 1l. This burner has a block 43, the upper face of which is provided with two annular recesses 44 and 45. A plate 45 secured to the block [i5 in any suitable way covers these recesses and forms two annular gas distributing chambers to one of whichfone of the gases is delivered by means of a conduit 4l and to the other of which the second gas isv delivered by means of a conduit 45. The lower face of the block 43 is provided with a shallow circular recess. A block 49 covers this recess so that there is formed a flat circular space having the above-mentioned critical dimension d that constitutes a slot passage 5S for the gases. A circular series of discharge passage or passageways 5l lead from the slot passage 55 to the discharge face 45a of the burner. Acircular series of supply passages 52 place the annular gas distributing chamber t4 in communication with the slot passage 53 radially outward of the circumference of the circle along which the discharge passages 5I join the slot passage, and another series of similar supply passages 53 place the annular distributing chamber 45 in communication with the slot passage 56 radially inward 0f such circumference. Thus, one of the gases passes radially inward through a. portion of the slot passage 55 and the other gas passage passes radially outward through a portion of it until they meet at the entrance to the discharge passages 5i and then flow down through the discharge passages in which they are further mixed.

Still another type of burner in which the gases mix in the discharge passages is illustrated in Fig. 12. In this case the narrow slot passage of critical dimension 54 is in the form of an annular space whose axis is parallel to the discharge face 55 of the burner. A row of discharge passages or passageways 55 (only one of which appears in Fig. 12) lead from the annular slot passage 54 to the discharge face of the burner. The two gases to be mixed are delivered separately to distributing chambers 51 and 5S. A row of supply passages extend from the distributing chamber' 5l and communicate with the annular slot passage 54 at the left side thereof as viewed in Fig. 12, one of these supply passages being shown at 59. Similar supply passages extend from the distributing chamber 55 and communicate with the annular slot passage 54 at the right side thereof as viewed in Fig. 12. One of these supply passages is shown at 50 in Fig. 12. Thus the two gases are delivered separately to the annular slot passage and flow separately around its opposite sides. They meet at the entrance to the discharge passages 56 and mix at this point and as they flow through the discharge passages.

The burner illustrated in Figs. 13 and 14 has a circular slot passage 6I similar to the one shown in Fig. 10 and a single discharge passage or passageway 62 leading from the center of the circular slot passage to the discharge face of the burner. The burner has annular gas distributing chambers 63 and 54 and gas supply passages 65 and B6 leading from them and communicating with the slot passage 6| radially outward of the discharge passage B2. The two gases therefore mix in the slot passage 6I before they reach the discharge passage 62. In this respect the gas passage arrangementv is similar to that employed in the burner illustrated in Figs. 7 and 8.

A burner oi the slot-mixing type having an annular slot passage 61 and discharge passages or passageways 58 of the type shown in Fig. 12 is illustrated in Fig. 15. This type of burner has two oxygen distributing chambers 69 and 'Hl and a single acetylene distributing chamber 'H as in the case of the burner shown in Fig. 7. A row of oxygen supply passages lead-from the oxygen distributing chamber 69 to the left of the annular slot passage 5'! as viewed in Fig. 15, one of these passages being shown at 12. A row of similar supply passages lead from the oxygen distributing chamber 'I0 to the right side of the annular slot passage 54 as viewed in Fig. 15, one of these passages being shown at '13. Two rows of acetylene supply passages 'i4 and 'i5 lead from the acetylene distributing chamber 'H to the annular slot passage 54, the passages of one row joining the annular slot passage at its left side as viewed in Fig. 15, and those of the other row joining the annular slot passage at its right side. Thus, although the two gases are delivered separately to each side of the annular slot passage, they mix as they ow around the opposite sides of the annular slot passage and are already mixed by the time they reach the entrance to the discharge passage 63. y

It will now be seen that in all forms of the improved burner above described the oxygen and fuel-gas are delivered separately to a slot passage located just upstream of the final discharge passage or passages leading to the discharge face of the burner, which slot passage has the abovementioned critical dimension at or below which a mixture of the gases cannot burn in the slot passage. The slot passage may not stop flame propagation or detonation, but it does prevent the continued burning of a gas mixture within it or at the entrance to the discharge passage or passages. While the gases may mix either in the slot passage or in the discharge passage or passages, no gas mixture is present upstream of the slot passage. Since the slot passage is too narrow to allow burning of the gas mixture within it, and the gas velocity at the entrance to the discharge passage or passages is too high to allow burning of the gas mixture there, and since discharge passages are employed that have TiI sufliciently smooth walls' to prevent a name from hanging in them, the gas mixture is. allowed to burn only` at the discharge end of the discharge passage or passages, i. e. at the discharge face of the burner. The invention therefore provides a ashback-proof burner and mixer unit. Backfire is controlled because of the` small mixed gas volume and the burner is therefore substantially non-popping." This is particularly true. of a multi-flame burner having a passage arrangement of the type illustrated in Figs. 4, 5, 6 and 9 and which cannot spatter molten metal from a weld puddle by a large gas volume backfire because backfire occurs only in those discharge passages that are disturbed in some way, whereas in multiname tips in which all of the discharge passages are supplied from a common source of mixed gases backfire will occur in all of the discharge passages if one is disturbed. rlhe improved burner is selfcleaning because it will clean itself of dirt and carbon Vby artificially induced backfire. Since the burner is flashback-proof it can be artificially caused to backfire in rapid succession, blowing out all of the foreign matter from the passages, and also burning all combustibles, thus eliminating the use of cleaning devices. The burner produces a stable flame and can be operated -successfully with a wide range of gas'iiows to produce neutral, carburizing or oxidizing flames. In fact, when the burner is of the multi-flame type andY has a gas passage arrangement such as shown in Figs. 4, and 6, a single burner may be caused to provide neutral, carburizing and oxidizing names simultaneously. This may be accomplished, for example, by making the oxygen port or ports leading to one of the slot passages 28 or 28" larger than the acetylene port or ports leading to the same slot passage, and giving the oxygen and acetylene ports leading to an adjacent slot passage the reverse proportions or giving them the same size. Moreover, one multillame burner, if desired, can have discharge orifices of various sizes.

In the slot-mixing type of the burner shown in Figs. 7-9 and 13-15 it makes no difference which gas is introduced to the slot passage on the upstream side. This makes it possible to use the gas passages leading to the slot passage interchangeable for either oxygen or acetylene in this type of the burner as well as in all forms of thedischarge-passage-mixing type except the special form of multi-flame burner described in the last paragraph adapted to provide different types of flames simultaneously.

The terms of orientati-on and direction used in the foregoing description apply to the various forms of burner when they are used in the vertical position, i. e., with the flame jets directed downwardly, but it should be understood they may be used in any position. f

In our co-pending application Serial No. 82,314, nled March 19, 1949, we have claimed a flashbackproof gas mixer embodying certain features of the gas burner claimed herein.

We claim: Y

l. An anti-flashback multi-flame gas burner comprising a burner block having separate inlet passageways for thefuel gas and the combustionsupporting gas, a discharge face, a plurality of discharge passageways. leading to the discharge face and terminating in separate discharge orifices, said discharge passageways having a smooth surface throughout, said burner block having a narrow slot upstream from said discharge passageways and communicating there-v with, and means for delivering gases from said separate inlet passageways to said slot at locations such that each gas must flow through a portion of the slot in a direction parallel to the opposing walls which define the narrow dimensions of the slot before reaching the entrance to the respective discharge passageways, the dimension of the slot in one direction transverse to the direction of the flow of gases through the slots not exceeding about .016 inch at any place and being suinciently narrow that burning of the gases introduced through the respective inlet passageways and passing through the slot to the discharge passageways will not be sustained in the slot, the walls defining the slot having a thickness greater than the width of the slot and also having suiiicient mass and heat-absorbing capacity to cool burned mixed gases passing therethrough on a backre suiicient to prevent flashback, all of the dimensions of said discharge passageways being relatively large compared to said dimension of the slot.

2. An anti-flashback gas burner as set forth in claim 1 in which the discharge passageways lead froman intermediate portion of said slot and the gases from the respective inlet passageways are delivered to the slot at opposite sides of the place vhiere the discharge passageways lead from the s o 3. An anti-nashback gas burner as set forth in claim 1 in which the slot is in the form of an annular space.

4. An anti-flashback gas burner as set forth in claim 1 in which the slot is in the form of a circular fiat space.

5. An antiflashback gas burner as set forth in claim 4 in which the discharge passageways of the burner are arranged in a circular series and the gas from one of the inlet passageways is delivered to the slot radially inward of the circumference along which the circular series of discharge passageways join the slot, and the gas from the other of the inlet passageways is delivered to the slot radially outward of said circumference.

6. An anti-flashback multi-flame gas burner comprising a burner block having separate inlet passageways for the fuel gas and the combustion-supporting gas, a discharge face, a plurality of discharge passageways leading to the discharge face and terminating in separate discharge oriiices, said discharge passageways having a smooth surface throughout, said burner block having narrow slots upstream from said discharge passageways and communicating therewith, and means for delivering a gas from one of said inlet passageways tol one of said slots, means for delivering a gas from" the other of said inlet passageways to another of said slots, the gases from the inlet passageways being delivered to therespective slots at locations such that each gas mu-st flow through portions of said slots in a direction parallel to the opposing walls which define the narrow dimensions of the slots before reaching the entrance to said discharge passageways, the dimension of the slots in one direction transverse tov the direction of the now of gases through the slots not exceeding about .016 inch at any place and being sufficiently narrow that burning of the gases introduced through the respective inlet passageways and passing through the slots to the discharge passageways will not be sustained in the slots, the walls defining the slots having a thickness greater than. the width of the slots and yalso having suiiicient mass and heat-absorbing- @e capacity to cool Vburned mixed' gases passing throughthe slots on a backre sufcient to prevent flashback, all of the dimensions of said discharge passageways being relatively large compared to said dimension of the slot.

7. An anti-flashback multi-flame gas burner comprising a burner block having separate inlet passageways for the fuel gas and the combustion-supporting gas, a discharge face, a plurality of discharge passageways leading to the discharge face and terminating in separate discharge orifices, said discharge passageways having a smooth surface throughout, said burner block having narrow slots upstream from said discharge passageways and communicating therewith, means for delivering gases from each of said inlet passageways to each of said slots at locations such that each gas must flow through a portion of each slot in a direction parallel to the opposing walls which define the narrow dimensions of the slots before reaching the entrance to said discharge passageways, the dimension of the slots in one direction transverse to the direction of the flow of gases .through the slots not exceeding about .016 inch at any place and being sufciently narrow that burning of the gases introduced through the respective inlet passageways and passing through the slots to the discharge passageway will not be sustained in the slots, the walls defining the slots having a thickness greater than the width of the slots and also having sufficient mass and heat-absorbing capacity to cool burned mixed gases passing through the slots on a backfire sui'licient to prevent flashback, all of the dimensions of said discharge passageways being relatively large compared to said dimension of the slot. i

8. An anti-ashback multi-flame gas burner comprising a burner block having a burner face, a plurality of smooth-walled discharge passageways leading to the discharge face and terminating in separate discharge orifices, separate means for supplying fuel gas to each individual discharge passageway, and separate means for supplying combustion-supporting gas to each individual discharge passageway, said fuel-gas supply means and said combustion-supporting gas supply means having restricted passages with a dimension in one direction transverse to the direction of gas ow therethrough not exceeding about .O16-inch at any place, said restricted passages discharging directly into said discharge passageways, all of the dimensions of said discharge passageways being relatively large compared to said dimension of the slot.

9. An anti-flashback multi-flame gas burner comprising a portion having a discharge face, a plurality of discharge passageways leading to the discharge face, a plurality of supply passageways for a fuel gas, a plurality of supply passageways for a combustion-supporting gas, said burner having a plurality of narrow slots upstream of said discharge passageways, each of said slots having a dimension in one direction transverse to the direction of the flow of gases through the slots not exceeding .016 inch at any place and sufciently narrow that burning of the fuel and combustion-supporting gases introduced through the respective supply passageways and passing through the slots will not be sustained therein, each of said slots placing one of the discharge passageways in communication with one supply passageway for the fuel gas and one supply passageway for the combustion-supporting gas, the walls dening the slots having thicknesses aeieaa l0 l greater than the width of the slots and also having sufficient mass and heat-absorbing capacity to cool burned gases passing through the slots on a backfire sufficient to prevent iiashback, all of the dimensions of said discharge passageways being relatively large compared to said dimension of the slot. Y Y

1G. An anti-flashback multi-flame gas burner comprising a portionv having a discharge face, a plurality of discharge passageways leading to the discharge face, a plurality of supply passageways for a fuel gas, a plurality of supply passageways for a combustion-supporting gas, said burner having a plurality of narrow slots upstream of said discharge passageways, the dimension of the slots in one direction transverse to the direction of the flow of gases through the slots not exceeding .O16 inch at any place and sufhciently narrow that burning of the fuel and combustion-supporting gases introduced through the respective inlet passageways and passing through the slots will not be sustained therein, each of said slots placing one of the discharge passageways in communication with two supply passageways for the fuel gas and two supply passageways for the combustion-supporting gas, the walls defining the slots having thicknesses greater than the width of the slots and also having suflicient mass and heat-absorbing capacity to cool burned gases passing through the slots on a backfire sufficient to prevent flashback, all of the dimensions of said discharge passageways being relatively large compared to said dimension of .the slot.

1l. An anti-flashback multi-fiance gas burner comprising a portion having a discharge face, a plurality of discharge passageways leading to the discharge face, a plurality of supply passageways for a fuel gas, a plurality of supply passageways for a combustion-supporting gas, said burner having a plurality of narrow slots upstream of said discharge passageways, the dimension of the slots in one direction transverse to the direction of the iiow of gases through the slots not exceeding .016 inch at any place and sufciently narrow that burning of the fuel and combustion-supporting gases introduced through the respective inlet passageways and passing through the slots will not be sustained therein, each of said slots placing two of the discharge passageways in communication with one supply passageway for the fuel gas and one supply passageway for the combustion-supporting gas, the walls defining the slots having thicknesses greater than the width of the slots and also having sufficient mass and heat-absorbing capacity to cool burned gases passing through the slots on a backfire suiicient to prevent flashback, all of the dimensions of said discharge passageways being relatively large compared to said dimension of the slot.

l2. In an ariti-iiashback multi-flame glas burner apparatus having a fuel gas inlet and a separate combustion-supporting gas inlet; a gas passageway in the form of a slot, the dimension of the slots in one direction transverse to the direction o1' the flow of gases through the slots not exceeding about .016 inch at any place, conduit means for admitting fuel gas from said fuel gas inlet to a point in said slot, conduit means i'cr admitting combustion-supporting gas from said combustion-supporting gas inlet to another point in said slot, a discharge face, a plurality of discharge passageways communicating with said slot at points intermediate said other points and leading to the discharge face and terminating in separate discharge orifices to permit gas to be dis- 11 charged from said slot through said burger 91j;- cs, said' dis/charge passageways being `srl/1190811- Walled vholes'of uniform cross section, all of the dimensonsof said discharge passageways 'being relatively large compared to said dimension of the slot.

LEWIS D. CONTA.

JOHN TETI.

EFERENCEs CITED The followingr references are of record in the file of this patent:

Number 912 UNITED-STATES PATENTS :N'm Date Anderon -ff: f Apr'. 8, 1919 .Knudson 50ct. 2,1, 1919 Cuwin -4---.: 1.? Sept.V 1,. 1936 Jacobsson v l ..v r `1leb. 22, 1938 Jonesr et, al. 2-112-- May 20. 1941 Young Julyl, A1941 Oldham ff- V-f--a May 16, 194:4 Robbins et 111.- --A-' June 1 1948 Thurman Oct. 4, 194.9 

